Electric rectifying device



Dec. 31, 1929. M. LAZARUS- 1,741,319

' znscnuc RECTIFYING DEVICE Original Filed Sept. 1.1928

I B? I I :INVIENTOR.

ATTORNEY.

. Patented Dec. 31, 1929' PATENT OFFICE MEYER nnznnnsQor BROOKLYN, NEWYORK ELECTRIC RECTIFYING DEVICE I riginal application filed September 1,

12, 1929. Serial No. 385,228.

In a well-known type of electric valve or rectifying device of the drytype, embodying as an element a copper plate provided m with a layer ofcuprous oxide as the means for securing the desired uni-directional flowof current, difiiculty has been experienced in producing valves ofuniform operation in practice, and yielding a high ratio -,betweentransmissioninone direction and obstruction in the other direction, andthis difficulty has been attributed to various causes, includingimproper preparation of the obstructive layer, insufficien-t contactbetween the component elements and other causes of a latent characterwhich have heretoifore been unidentified and which have persistentlycaused failure of many-such valves to function in theintended manner.

I have discovered by extended experiments of a widely varied character,that a primary defect in such valves arises from the use of a copperelement which is not of a character adapted coco-operate with thecuprous oxide or equivalent obstructive layer in securing theobstructive eiiect and in permitting the free uni-directional flow, andan important achievement of the presentinvention is to provide apositive element consisting of an alloy of copper with silverinproportions which I have discovered to be adapted to serve in anunexpected manner and afford to an unforeseen degree the desiredhigh'ratio of reversibility or differential between freedom of flow inone direction and obstruction to flow in the opposite direction, andwhich can be readily'embodied commercially in electrical valve elementsthat exhibit a uniformity in operation which makes these valvesthoroughly dependable in practice.

A further defect which .I have remedied results from the fact that ifthe rectifying plates of which such an electric valve is composed arenot made uniform, some of the plates will have a lower resistance andthese.

plates will carry more current than the adjoining plates having a higherresistance and will become overheated and burn out. By

the provision of an alloy of copper and silver in predeterminedproportions I am enabled to insure a more homogeneous and uniformcomposition 'for the rectifying plates than has been attainedheretofore.

A further object of the invention is to provide a positive rectifyingelement having such a'copper-silver alloy base with a rectifying layerof oxide of copper and oxide of sllver, which constitutes a novel andhighly efficient obstructive layer.

Another object is to form an electric valve having such a. c0pper-silveralloy base and rectifying layer with a metallic surface film of copperand silver.

Still another. object is to provide a rectifying element having theforegoing characteristics with a surface coating of tin or the like andthereby to furnish a tough, uniform facing which will always stay cleanand afford a good mechanical and electrical contact g for theco-operating negative element.

Another object is to form electric valves having an element of sheetmetal such as copper and an obstructive layer by a process whichcomprises as a novel step heating said metal in an atmosphere containingozone in quantities greater than those common to atmospheric air, andthereby forming an obstructive layer thereon characterized by a uniformgrain and ox-blood color.

The above, and other, features of the invention are illustrated anddescribed fully in the accompanying drawings and specification, and arepointed out in the claims.

In the drawings, the figure shows at l a now-preferred form ofrectifying plate or element in the formation of which my invention hasbeen carried into effect. The plate is of particular utility when usedin electricvalves or rectifying devices of the dry type,

and certain of the; features thereof form the subject of claims in myco-pending application Ser. No. 303,583, from which my presentapplication has been divided.

The body of the plate illustrated is designated by thereferencecharacter 6, and in 1928, Serial no. 303,533. Divided at thisapplication filed August pursuance of an im ortant object of the presentinvention I pre or to form this body por tion of an alloy of copper andsilver which I have discovered by extended experiments to be capable ofaffording the freest possible transmission of current in the desireddirec tion, on the one hand, and upon which is formed an obstructivelayer comprising cuprous oxide and oxide of silver in combination, asthe preferred rectifying medium,.inasmuch as the same constitutes anovel and improved element affording'the greatest obstruction to' flowof current in the reverse direction, thus obtaining the maximumdifferunderstood from the followingdescription of the results observedin the practice of the invention.

I find in practice that upon the addition of even a few ounces of silverto pure copper, or copper of ordinary commercial purity, say in theproportion of 5 ounces or less of silver to a ton of copper, thereresults a certain increase in conductivity in one direction and arelatively very high increase in the obstructive effect yielded to flowof current in the opposite direction, so that a desirably higherrectifying ratio is at once established, as compared with copper notcontaining silver.

With each small increase of silver content in such a copper-silveralloy, there is an increase in conductivity for current withoutsubstantial change in obstructive effect, so that the rectifying ratioincreases rapidly .until the silver content reaches the proportion ofapproximately 25 to 40 ounces of silver to a ton of copper, which givesthe maximum rectifying ratio.

- ounces to a ton the rectifying" ratio remains With a silver content ofeven more than 40 desirably high, but the obstructive effect between thecopper-silver base, and the obstructive layer of copper-oxideand'silver-oxide thereon, decreases more noticeably as the proportion ofsilver is increased over 40 ounces to the ton of copperin the alloybase, so that the rectifying ratio is not so favorable, in comparisonwith-that secured with a silver content of 25 to 40.

With a silver content-of over 45 ounces'to the ton, the obstructive efiect diminishes more rapidly under ordinarygconditions, and the increasein conductivity in-the other direction becomes less important,ord1nar1ly, al-

though under some conditions when a high rectifying vratio is lessimportant than high conductivity, the proportion of silver may beincreased to the extent found desirable for any given service.

A copper-silver alloy having a unifbrmly distributed silver content ofless than 5 ounces of silver to the ton, accordingly, may give anenhanced and reliable obstructive efect, which is however lacking inserviceable quality, because the conductivity is too lowto yield 'adesirably high rectifying ratio, and such an alloy in which the silvercontent amounts to 50 ounces to the ton will ordinarily not beserviceable because the conductivity has been increased at the expenseof diminishing the obstructivity effect, and thus again lowering therectifying ratio.

The rectifying plates are respectively provided with an obstructivelayer 7, preferably on each surface of the body 6, although only oneside is shown by Way of illustration, and the obstructive layermay beofany suitable character for the intendedpurpose, such as the novel layerof combined cuprous oxide and oxide of silver already referred to, whichI regard as the preferred form.

In forming an obstructive layer of copper oxide with silver oxide, Iprefer to utilize the novel process to which reference has already beenmade, and which includes the step of heating the plates in an atmospherecontaining ozone in quantities greater than those common to atmosphericair, as for example in an electric furnace, for a suitable time untilthe layer of cuprous and silver oxide is formed, and then holding themin the air urftil they come to a cherry red color',-and then plungingthem quickly into a bath of'water and aleohol,or 'water and glycerine,with a surface layer of oily liquid, such as turpentine or a liquidhaving a phenolic or cresolic composition.

I find that with the use of ozone thus an excellent cuprous and silveroxide is formed, characterized by a uniform grain and oxblood color, andthe quenching treatment in a bath with an oily surface layer has theeffect of annealing the obstructive layer, and may also be utilizeddesirably to reduce part of type above described, but other suitablemethods of providing such a film may be utilized, as the particularmethod described is not indispensable.

In further pursuance of this object of my invention, I prefer to providethe rectifying plate with a protective layer or coating 9,

of suitable metal, such as tin, by any suitable plating method, and thusfurnish a tough, uniform facing which will always stay clean and afforda good electrical and mechanical connection with. the metallic film ofcopper and silver above described as having been formed on the surfaceof the copper and silver oxide, or the protective layer of tin or thelike may be applied to plates having an oxide layer .without a film ofmetallic copper and silver.

. As one convenientform of my improved rectifying plate, or positiveelement, I have shown in the drawing a plate'having lugs 11, tofacilitate its connection, mechanically and electrically, in assemblinga valve unit comprising a series of said plates, the plate having alsolation. subject of claims in my aforesaid application, tier. No.303,583. I

I claim:

1. An electric valve or rectifying device of the dry type, adapted topermit free flow of current in one direction, but to obstruct flow ofcurrent in reverse direction, said device 'of current in one beingcharaterized by a positive element comprising an alloy of copper withsilver, and provided with. a rectifying layer.

2. An electric valve or rectifying device ofthe dry type, adapted topermit free flow direction, but to obstruct flow of current in reversedirection, said device being by a positive element comprising an alloyof copper with silver and having an obstructive layer comprising anoxide of copper and an oxide of silver.

3. An electric valve or rectifying device of the.,dry type adapted topermit free flow of current in one direction, but to obstruct flow ofcurrent in reverse direction, said device being characterized by apositive element comprising an alloy of copper with silver in theproportion of ap to fort per, said element having a rectifying layer.

'4. electric valve or recti ing device of the dry type adapted to permitfree flow of having an element of acentral aperture to permit venti-These mechanical features form the.

or current in reverse direction, said device being characterized by apositive element comprising an alloy of copper with silver in theproportion of approximately twenty-five to forty ounces of silver to oneton of copper,

and having an obstructive layer comprising an oxide of copper and anoxide of silver. 5. An electric valve or rectifyin device of the drytype adapted to permit ree flow of. current in one direction but toobstruct flow of current in reverse direction, said device beingcharacterized by a positiveelement comprising an alloy of copper withsilver and having an obstructive layer comprising an oxide of copper andan oxide of'silver, said obstructivelayer having a metallic surface filmof copperand silver. I

6. An electric valve comprising a rectifying plate comprising an alloyof copper and silver, having on each face an obstructive layerof copperoxide and silver oxide, and a surface coating of tin or the like. 7. Anelectric valve comprising a rectifying plate comprising an alloyofcopper and silver, having on each face an obstructive layer of copperoxide and silver oxide, a metallic film of said alloy and a surfacecoating of tin or the like.

8. In the process of forming electric valves sheet metal such as and anobstructive layer, the step which comprises heating. said metal in anatmosphere containing ozone in quantities greater than those commonto.atmospheric air, and thereby forming an olbstructive layer of oxidethereon.

In testimony whereof, I. have signed th s specification.

MEYER LAZARUS.

copper roximately twenty-five I ounces of si ver to one ton of cop- I yno

